9,450 research outputs found
Planning the integration of ex situ plant conservation in Tasmania
Tasmania has a strong record of successful in situ plant conservation but there will always be a role for the integration of various ex situ measures into a plant conservation program due to pressure by threatening processes on wild populations. This paper replaces a 15 year old strategy for ex situ conservation in Tasmania. Progress in ex situ measures for Tasmanian plants is described and broadly evaluated against the previous strategy. Rare and threatened species are considered to be a high priority group for resources if intensive management is required. Endemic species likely to be adversely impacted by climate change would be a high priority for ex situ conservation. Seed banking to capture as much genetic variation in these species is suggested. Eight ex situ methods are briefly described and their application in Tasmanian instances noted. The Tasmanian Seed Conservation Centre established at the Royal Tasmanian Botanical Gardens is a central part of Tasmanian ex situ conservation efforts for ex situ conservation programs. An ongoing role for this facility is considered fundamental
An anti-symmetric exclusion process for two particles on an infinite 1D lattice
A system of two biased, mutually exclusive random walkers on an infinite 1D
lattice is studied whereby the intrinsic bias of one particle is equal and
opposite to that of the other. The propogator for this system is solved exactly
and expressions for the mean displacement and mean square displacement (MSD)
are found. Depending on the nature of the intrinsic bias, the system's
behaviour displays two regimes, characterised by (i) the particles moving
towards each other and (ii) away from each other, both qualitatively different
from the case of no bias. The continuous-space limit of the propogator is found
and is shown to solve a Fokker-Planck equation for two biased, mutually
exclusive Brownian particles with equal and opposite drift velocity.Comment: 19 pages, 5 figure
The release of a captive-raised female African Elephant <em>(Loxodonta africana</em>) in the Okavango Delta, Botswana
Wild female elephants live in close-knit matrilineal groups and housing captive elephants in artificial social groupings can cause significant welfare issues for individuals not accepted by other group members. We document the release of a captive-raised female elephant used in the safari industry because of welfare and management problems. She was fitted with a satellite collar, and spatial and behavioural data were collected over a 17-month period to quantify her interactions with the wild population. She was then monitored infrequently for a further five-and-a-half years. We observed few signs of aggression towards her from the wild elephants with which she socialized. She used an area of comparable size to wild female elephants, and this continued to increase as she explored new areas. Although she did not fully integrate into a wild herd, she had three calves of her own, and formed a social unit with another female and her calf that were later released from the same captive herd. We recommend that release to the wild be considered as a management option for other captive female elephants
The Semantic Web as a Semantic Soup
The Semantic Web is currently best known for adding metadata to web pages to allow computers to 'understand' what they contain. This idea has been applied to people by the Friend of a Friend project which builds up a network of who people know through their descriptions placed on web pages in RDF. It is here proposed to use RDF to describe a person and to have their RDF document follow them around the Internet. The proposed technique, dubbed Semantic Cookies, will be implemented by storing a user's RDF in a cookie on their own computer through the browser. This paper considers the concept of Semantic Cookies and investigates how far existing technology can be pushed to accommodate the idea
Testing for Stochastic Cointegration and Evidence for Present Value Models
Using the stochastic integration/cointegration framework of Harris, McCabe and Leybourne (2002) we revisit the problem of assessing the empirical evidence for or against the present value class of models in the bond and stock markets. This framework allows for volatility in excess of that catered for by the conventional integration/cointegration paradigm by introducing nonlinear heteroscedasticity. We propose a test for stochastic cointegration against the alternative of no cointegration and a secondary test for stationary cointegration against the heteroscedastic alternative. Asymptotic distributions of these tests under their respective null hypotheses are derived and consistency under their respective alternatives is established. In contrast to conventional cointegration tests, which we show via simulation are unreliable in the presence of the kind of volatility typical of financial data, our tests are able to uncover new cointegration evidence in favour of the present value model, particularly in the bond market.
Molecules in the mirror: how SERS backgrounds arise from the quantum method of images
The Raman coupling of light to molecular vibrations is strongly modified when they are placed near a plasmonic metal surface, with the appearance of a strong broad continuum background in addition to the normal surface-enhanced Raman scattering (SERS) peaks. Using a quantum method of images approach, we produce a simple but quantitative explanation of the inevitable presence of the background, due to the resistive damping of the image molecule. This model thus suggests new strategies for enhancing the SERS peak to background ratio
Development of models for predicting Torsade de Pointes cardiac arrhythmias using perceptron neural networks
Blockage of some ion channels and in particular, the hERG cardiac potassium
channel delays cardiac repolarization and can induce arrhythmia. In some cases
it leads to a potentially life-threatening arrhythmia known as Torsade de
Pointes (TdP). Therefore recognizing drugs with TdP risk is essential.
Candidate drugs that are determined not to cause cardiac ion channel blockage
are more likely to pass successfully through clinical phases II and III trials
(and preclinical work) and not be withdrawn even later from the marketplace due
to cardiotoxic effects. The objective of the present study is to develop an SAR
model that can be used as an early screen for torsadogenic (causing TdP
arrhythmias) potential in drug candidates. The method is performed using
descriptors comprised of atomic NMR chemical shifts and corresponding
interatomic distances which are combined into a 3D abstract space matrix. The
method is called 3D-SDAR (3 dimensional spectral data-activity relationship)
and can be interrogated to identify molecular features responsible for the
activity, which can in turn yield simplified hERG toxicophores. A dataset of 55
hERG potassium channel inhibitors collected from Kramer et al. consisting of 32
drugs with TdP risk and 23 with no TdP risk was used for training the 3D-SDAR
model.An ANN model with multilayer perceptron was used to define collinearities
among the independent 3D-SDAR features. A composite model from 200 random
iterations with 25% of the molecules in each case yielded the following figures
of merit: training, 99.2 %; internal test sets, 66.7%; external (blind
validation) test set, 68.4%. In the external test set, 70.3% of positive TdP
drugs were correctly predicted. Moreover, toxicophores were generated from TdP
drugs. A 3D-SDAR was successfully used to build a predictive model for
drug-induced torsadogenic and non-torsadogenic drugs.Comment: Accepted for publication in BMC Bioinformatics (Springer) July 201
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